MDMT x MDT x Impact Test

[Mateus_R]

Dear all,

For a project in Russia, I'm facing the following situation:

The scope of supply include this information in the section Design/Ambient Condition:
- Minimum design metal temperature: -44°C
- Minimum ambient temperature: -53°C

What I didn't understand is why the customer impose an MDMT if this value is calculated and can't be explicit defined?
They made confusion and what they are really asking is that the Minimum Desing Temperature is -44°C, and the MDMT is calculated based on this value? Am i wrong reasoning like this?

Saying that, where I include the -53°C in my analysis?

And related to the impact test, should I provide it for -44°C or -53°C?

Thanks in advance.

 

[gerhardl]

I have often experienced that technical text are unclear or conflicting.

One should not make guesses but go directly to the customer.

One way to ask if the simplest solution is satisfactory : We plan to use the design temperature - 44 deg. C as given, with impact test also at this temperature. Please inform if other tests, certifications or guaranties are necessary.

 

[Geoff13]

The MDMT is typically the Code required temperature, whereas minimum ambient can be pretty meaningless.

For example, API 650 allows you to assume the MDMT for a tank is 8°C above the low one day mean (LODM). This is in recognition of the fact that even if the ambient temp gets very cold for a day or two the tank contents will keep the tank shell slightly warmer.

Minimum ambient temp sounds like an instantaneous value and should be even colder than the LODM.